1. Field of the Invention
The present invention relates to a magnetic resonance imaging apparatus, and particularly to a magnetic resonance imaging apparatus for scanning a spine.
2. Description of the Prior Art
Magnetic resonance imaging (MRI) is an imaging technology for obtaining internal structural information of an object by means of the magnetic resonance phenomena. MRI is broadly used in the field of medical imaging due to its significant advantages, such as a large number of imaging parameters, high resolution, tomography in any layer required, non-destructive imaging, etc.
It is normally considered that if a surface coil is close to a patient, the image signal would be strong, the noise level low, the signal-to-noise ratio high, and the images relatively fine. When performing the magnetic resonance imaging on a human spine, a spine coil is usually used in order to obtain magnetic resonance images of relatively high qualities, and this makes it necessary to keep the coil sufficiently close to the human body. As to the spine coil, it is conventionally disposed on the upper surface of a patient table, and the patient lies on the spine coil for carrying out the imaging, as shown in FIG. 1.
FIG. 1 shows a longitudinal structural illustration of a prior art magnetic resonance imaging apparatus for scanning a spine, and FIG. 2 is the lateral structural illustration of the apparatus. In FIGS. 1 and 2, gradient coils 12 are embedded a magnet 11, a body coil 13 is on the inner wall of the magnet 11; a patient table 16 is located within the chamber of the magnet 11, and a spine coil 15 is arranged on the upper surface of the patient table 16. When performing a scan on a patient 14 lying on the patient table 16, actually the patient lies on the spine coil 15. The thickness of the spine coil 15 is usually about 40 to 60 mm.
During the process of scan-imaging, the relative movements between the patient 14 and the spine coil 15 are quite complicated. Therefore, when carrying out the scan, in order to obtain the scanned images of the whole spine of the patient 14 conveniently and promptly, the spine coil 15 is usually set to have a length equal to or slightly longer than the human spine, so that after a patient 14 has laid down on the patient table 16, the scanned image of the whole spine of the patient 14 can be obtained by one go without any movement.
Generally, the magnetic resonance imaging apparatus for scanning a spine in the prior art has following disadvantages:
1) the relative movement between the patient and the spine coil is impossible, so the spine coil needs to have a sufficient length in order to achieve the scan of a whole human spine, therefore the coil needs to use a large number of radio frequency component units, which lead to high costs;
2) as shown in FIG. 2, since there is the spine coil between the patient and the patient table, it leads to the reduction of the distance HI between the inner wall of the upper part of the emitting body coil and the patient, resulting in a narrow space for the patient, and reducing the patient's comfort; and
3) since there exists certain coupling between the spine coil and the emitting body coil, it is necessary to unplug the spine coil when the apparatus is not in operation and to re-plug it into the corresponding socket for next operation. Such repeated plugging and unplugging increases the probability of damaging the coil, and therefore affects the reliability of the coil and the imaging quality of the apparatus.
Currently, a common solution is to embed the spine coil into the board of the patient table, but by doing so the structural complexity of the board of the patient table is increased, and at the same time during its use the coil is still subject to factors such as the patient's body weight, etc., so the problem regarding vulnerability to damage still exists.